Need help understanding Shunt

mulia · May 2015

Hi,

I received my Whizbang Jr. along with 500A Shunt today. I'd like to install it to my Classic. Read the manual, I stuck with installing shunt.

I refer to whizbang manual, one side of shunt with purple cable along it (let's call it A side) should be connected to battery neg side while other (B side) should be connected to inverter/cc/load.

Attachment not found.

I've several questions regarding this:

1) Which one I need to connect to B side, inverter or CC? or both of them?

2) Can it be used to measure power generated by solar panel which go into batteries while also measuring power draw by inverter? More, if it's possible to measure power draw by cc. If it can, how do I need to wire them to work properly multitasking? (or I need another shunt)

3) I browsed through and found out article stating that negative terminal of batteries which connect to shunt should not also be used to take any load/charge. I wonder if this is true?

I found an image on web about this Load/no load.on shunt terminal.

Attachment not found.

I also wonder what's being measured here on image above. Is that power draw by system or power charged into battery.

Thank you.

BB. · May 2015

mulia wrote: »

Hi,

I received my Whizbang Jr. along with 500A Shunt today. I'd like to install it to my Classic. Read the manual, I stuck with installing shunt.

I refer to whizbang manual, one side of shunt with purple cable along it (let's call it A side) should be connected to battery neg side while other (B side) should be connected to inverter/cc/load.

Attachment not found.

I cannot really make out much detail in the attachments...

I've several questions regarding this:

1) Which one I need to connect to B side, inverter or CC? or both of them?

The standard method is to connect one side of the shunt to the battery negative terminal, and the other side to the negative battery bus. This ensures that all battery current (charging and discharging) flows through the shunt. Therefore, the shunt is measuring current into the battery (charging + battery losses) and discharging (current exiting the battery).

Note that none of this directly measures the output of the charger or the loads--It measures:

Current through shunt = Charging Current - Load Current

If charging current = 0 amps, then Shunt Current = Load Current... And if loads = 0 Amps, then Charging Current = Shunt Current

2) Can it be used to measure power generated by solar panel which go into batteries while also measuring power draw by inverter? More, if it's possible to measure power draw by cc. If it can, how do I need to wire them to work properly multitasking? (or I need another shunt)

No--Other than specific conditions where Charging or Loads = Zero Current, the Battery Monitor is only measuring actual current into/out of the battery bank.

If you want to know, for example, how many Amp*Hours/Watt*Hours the charge controller produced in a day, then you need to use the CC's logging functions (or add a shunt to the charge controller).

And if you wan to know the loads (AC inverter), again, you have to use the Inverter's logging or add a DC shunt, or an AC logger (like a Kill-a-Watt meter or similar).

Note for off grid systems... A charge controller only measures Amp*Hours / Watt*Hours produced by the CC and "consumed" by battery charging + Loads. If you have a full battery bank and no loads, the CC will show near zero Amp*Hours produced--Even though the solar array could have produced hundreds of Amp*Hours worth of current.

Only if if loads + battery charging current equals or exceeds the solar array capabilities, will the charge controller show how much power the array would produce.

3) I browsed through and found out article stating that negative terminal of batteries which connect to shunt should not also be used to take any load/charge. I wonder if this is true?

If you put a 100 Watt bulb from battery + to battery -, no light bulb current will flow through the shunt--And therefore, the Battery Monitor "will be blind" to the light bulb's draw from the battery bank.

Note that during battery charging, the Batter Monitor will log the replacement current--But the battery bank will look like it is less efficient (more AH in than AH out).

I found an image on web about this Load/no load.on shunt terminal.

Attachment not found.

I also wonder what's being measured here on image above. Is that power draw by system or power charged into battery.

From what I can see, this is a traditional Battery Monitor + Battery Shunt installation.

Remember that battery monitors are keeping track of battery state of charge and battery usage... It is not (directly) measuring the loads or charging currents.

Sort of like a gas gauge in the car... It only knows the fuel level in the thank... If you are running the engine and filling the tank at the same time (say you have an extra fuel tank and a transfer pump)--The gas gauge only shows the fuel tank level--Nothing more or less.

Of course at night, the BM does show what the loads are doing (no solar charging current sources).

-Bill

westbranch · May 2015

to use the WhizBang jr you will also need either a Classic or Kid charge controller. With one of those CC's you will get more info than you will be able to understand. I have a Classic and it saves data internally and you can download that to get what you are after. If you have a laptop or tablet you can connect directly or rig a wifi connection to your computer I recommend you do some reading over on the MidNiteSolar.com site, look for FORUM near the top of the home page. There is a section dedicated to the WBjr...
happy reading

BB. · May 2015

Here is the Midnite Forum link:

http://midnitesolar.com/Forum/

-Bill

mulia · May 2015

The standard method is to connect one side of the shunt to the battery negative terminal, and the other side to the negative battery bus. This ensures that all battery current (charging and discharging) flows through the shunt. Therefore, the shunt is measuring current into the battery (charging + battery losses) and discharging (current exiting the battery).

Note that none of this directly measures the output of the charger or the loads--It measures:

Current through shunt = Charging Current - Load Current

If charging current = 0 amps, then Shunt Current = Load Current... And if loads = 0 Amps, then Charging Current = Shunt Current

Negative battery bus? Is that different from Negative battery terminal?

I just read the midnite forum, one post I read was suggesting like wbjr manual said, it's to hook a negative battery terminal on one side and inverter+cc negative on other side of shunt. I wonder if this is right.

Remember that battery monitors are keeping track of battery state of charge and battery usage... It is not (directly) measuring the loads or charging currents.

Sort of like a gas gauge in the car... It only knows the fuel level in the thank... If you are running the engine and filling the tank at the same time (say you have an extra fuel tank and a transfer pump)--The gas gauge only shows the fuel tank level--Nothing more or less.

Of course at night, the BM does show what the loads are doing (no solar charging current sources).

So, this whizbang jr. while connected to shunt with one side to negative battery and other to cc and inverter will show battery SOC and usage only? or it will also show another info?

I think it's better for me to hook up WBJR and the shunt first and see what I understand/don't understand before asking another question. Although I prefer to have a better understanding first.

to use the WhizBang jr you will also need either a Classic or Kid charge controller. With one of those CC's you will get more info than you will be able to understand. I have a Classic and it saves data internally and you can download that to get what you are after. If you have a laptop or tablet you can connect directly or rig a wifi connection to your computer I recommend you do some reading over on the MidNiteSolar.com site, look for FORUM near the top of the home page. There is a section dedicated to the WBjr...
happy reading

Yes, I own a Classic 150, that's why I acquire a WBJR. Thanks for the info.

Mountain Don · May 2015

mulia wrote: »

Negative battery bus? Is that different from Negative battery terminal?

That's just a place where many different wires can all be connected to the negative battery terminal. Each wire with its own bolt so any one item can be disconnected, connected wothout bothering any of the other connected wires. One side of my shunt connects to the battery negative. The other end to a copper buss bar. The CC output, inverter connection and a few direct to a DC use wires all connect there.

The positive terminal of the battery bank also connects to a positive buss, for all the same reasons.

BB. · May 2015

mulia wrote: »

Negative battery bus? Is that different from Negative battery terminal?

I just read the midnite forum, one post I read was suggesting like wbjr manual said, it's to hook a negative battery terminal on one side and inverter+cc negative on other side of shunt. I wonder if this is right.

Yes, this is correct and just different wording for the same thing. I used "Bus" as the generic multi connection point for all load/charging/safety grounding point. Battery negative terminal(s) to other side of the bus only connections.

If there are any "load" connections made on the battery negative terminal side of the bus, the load shunt will not "see"/measure the current of that load that bypasses the shunt.

So, this whizbang jr. while connected to shunt with one side to negative battery and other to cc and inverter will show battery SOC and usage only? or it will also show another info?

I think it's better for me to hook up WBJR and the shunt first and see what I understand/don't understand before asking another question. Although I prefer to have a better understanding first.

The Whizbang Jr. shunt is there to measure current flow into/out of the battery bank. and is concerned about the "health" of the battery bank (state of charge, rate of discharge/charge). Of course, if you have no loads and solar array charging--That is the solar array charging current. If there is no charging and one load turned on--It will show that load's current.

-Bill

westbranch · May 2015

here is a video to watch...http://www.midnitesolar.com/video/videoPlay.php?video_ID=92&videoCat_ID=21
and this one http://www.midnitesolar.com/video/videoPlay.php?video_ID=100&videoCat_ID=21

mulia · May 2015

Mountain Don wrote:

That's just a place where many different wires can all be connected to the negative battery terminal. Each wire with its own bolt so any one item can be disconnected, connected wothout bothering any of the other connected wires. One side of my shunt connects to the battery negative. The other end to a copper buss bar. The CC output, inverter connection and a few direct to a DC use wires all connect there.

The positive terminal of the battery bank also connects to a positive buss, for all the same reasons.

Ah, I see. That's buss bar just like inside of my combiner box. Sorry, late catch here. They're very useful and help to ease connect and disconnect; Unfortunately, I can't find something good like that in here. Thank you.

BB. wrote: »

If there are any "load" connections made on the battery negative terminal side of the bus, the load shunt will not "see"/measure the current of that load that bypasses the shunt.

Bill, I wonder if this is the right way to connect it?

Attachment not found.

I also wonder if it's okay to have the shunt act as buss bar by stacking CC and inverter ring terminal into it, is it safe?

I'll need strong screw to screw down the shunt next to classic for sure.

westbranch wrote:

here is a video to watch...http://www.midnitesolar.com/video/vi...videoCat_ID=21
and this one http://www.midnitesolar.com/video/vi...videoCat_ID=21

Thank you, it helps.

BB. · May 2015

The picture is hard to see--But I believe that you have the shunt connected correctly in the drawing.

Yes, you can use one terminal of the shunt as the system negative bus connection--As long as everything fits on the terminal safely..

Of course, you are missing fuses/breakers on the positive leads (to charge controller, to inverter, etc.).

-Bill

mulia · May 2015

Sorry about the picture, I thought it's been "thumbnailed"

Attachment not found.
Ah yes, about the fuse, everything are 'fused' properly using breaker.

I tried to install it today, with no luck, already attached WBJR to Shunt and hook them up to Classic. I found out that the Shunt is using #10 bolt while my battery ring terminal is #8. :-s

I'll need to get #10 terminal change all those #8 into #10. Really inconvenient. Or I need to get a great buss bar like my combiner's one which is not available in my country.

By the way, I kind of wondering if this WBJR really works well, I mean, it's supposed to show SOC of the battery bank which capacity is inputted by user at first. What if the battery is not having its full capacity anymore. As they aged, their capacity are decreasing. I think WBJR won't "sense" if those batteries getting 'wrinkled' by ages...

I think those hydrometers perform better although I need to take it multiple times to ensure their accurateness and those acid really annoying...

westbranch · May 2015

when you get teh WBjr installed a d working, you can use the Local App to fine tune the SoC to match the hydrometer readings, it is a bit of trial ans error but can be done

zoneblue · May 2015

Your last drawing is correct. YOu want nothin else on the battery side but the battery. The purple wire should also be on the battery end of the WBjr. Using the local app, set aux2 to wbjr (auto). Under end amps tick "use shunt'. Set the EA figure to one that you determine experimentally as being the fully charge end amps. YOu do this by talking SG readings during absord until SG stops rising, and at that point the charge acceptance current is your EA. However be sure to add about a half amp to this to make sure it trips correctly, and set a fall back absorb time that is about an hour longer than it normally takes. Make sense?

mulia · May 2015

westbranch wrote: »

when you get teh WBjr installed a d working, you can use the Local App to fine tune the SoC to match the hydrometer readings, it is a bit of trial ans error but can be done

I see. They can work together that way. Thank you.

zoneblue wrote:

Your last drawing is correct. YOu want nothin else on the battery side but the battery. The purple wire should also be on the battery end of the WBjr. Using the local app, set aux2 to wbjr (auto). Under end amps tick "use shunt'. Set the EA figure to one that you determine experimentally as being the fully charge end amps. YOu do this by talking SG readings during absord until SG stops rising, and at that point the charge acceptance current is your EA. However be sure to add about a half amp to this to make sure it trips correctly, and set a fall back absorb time that is about an hour longer than it normally takes. Make sense?

Yes, it make sense. A bit of work to be done. But, it'll work. Thank you for your explanation.

Need help understanding Shunt

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